The giant glass pane shattered on the pavement below but miraculously no-one was injured in the incident on Leman Street.
One passer-by said: “There was no building or maintenance work going on at the office block so it seems the glass somehow came loose.
“It’s a really hot day so I don’t know if that had anything to do with it because the front of the office is an all-glass atrium.
“Luckily it didn’t happen on a weekday because the pavement would have been full at midday when it came down.
“I walk by here every morning to go to the gym so I was only a matter of minutes away from being underneath it.”
A police officer at the site told the Enquirer: “We just got a call saying the street was covered in glass. It’s a bit of a mystery what has happened.”